The present invention relates to an oil based green ink for a ball point pen and a ball point pen. More specifically, it relates to an oil based green ink for a ball point pen the color of which can be identified from the outside when it is filled into a transparent ink reservoir, and a ball point pen using the same.
In oil based green inks for a ball point pen, a green color tone has so far been obtained by toning with a blue dye and a yellow dye. In such case, in a ball point pen using an oil based ink whose ink reservoir has a diameter of about 3.5 mm or less, the visual color in the state where the ink is filled into the ink reservoir has a tone close to a nearly black color due to a small amount of the ink filled, and it is practically impossible to identify what color ink is filled thereinto from the outside of the ink reservoir. Further, there has been a problem that when the drawn lines thereby are spread by solvents and chemicals, a blue color and a yellow color are eluted and the green drawn lines disappear.
It has been recognized that a pigment is preferably used for improving durability thereof and, for example, a phthalocyanine green pigment giving a green color tone by itself is preferably used. However, in the case of a ball point pen using an oil based ink, a colorant in the ink has to be compounded in a larger amount as compared with that for, for example, markers, and therefore a visual color of the ink in which a phthalocyanine green pigment is dispersed in a high concentration is darkened and close to a nearly black color.
It is effective for obtaining a stable dispersion system in which the phthalocyanine green pigment is dispersed in a high concentration to treat the surface of the phthalocyanine green pigment with phthalocyanine pigment derivatives, and such method is widely used. However, dispersions of the phthalocyanine green pigment which is subjected to surface treatment with the phthalocyanine pigment derivatives have a darkened visual color due to an effect of the surface treating agents and are close to a black color. Accordingly, there has been a problem that a visual color of an ink using the above dispersion has been darkened as well and is close to a black color and it is difficult to observe a green color of the ink through a transparent or translucent ink reservoir and a transparent or translucent barrel of the ball point pen.
The present invention has been made in light of the problems described above, and an object thereof is to provide an oil based green ink for a ball point pen the color of which can be identified by visual observation through a transparent ink reservoir and a part of the barrel in the ball point pen which transmits light, and a ball point pen using the same.
Intensive researches conducted by the present inventors in order to solve the problems described above have resulted in finding that use of an ink in which a spectral reflectance (%) determined in the state where the ink is filled into an ink reservoir has a maximum value in a specific wavelength range and in which a ratio of maximum strength/minimum strength of the spectral reflectance falls in a specific range makes it possible to identify a color of the ink by visual observation through the transparent ink reservoir and the transparent barrel of the ball point pen. Thus, the present invention has been completed.
That is, the oil based green ink for a ball point pen of the present invention is characerized by comprising at least one organic solvent selected from the group consisting of alcohols and glycol ethers, a resin and a colorant, wherein the spectral reflectance determined in the state where the ink for a ball point pen is filled into an ink reservoir has a maximum value in a wavelength range of 500 to 520 nm, and a ratio of maximum strength/minimum strength of the spectral reflectance is 2.2 to 5.5.
The ball point pen of the present invention is characterized by using the oil based greenink for a ball point pen described above.